462 



CHOLERA 



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Fig. 136. — Cholera spirilla stained to show 

 the terminal nagella. See also Plate IV., 

 Fig. 19. x 1000. 



They possess very active motility, which is most marked in 



the single forms, and 

 this is due to a single 

 terminal flagellum (Pig. 

 136). It is very delicate, 

 and measures four or 

 five \imes the length of 

 the organism. Cholera 

 spirilla do not form 

 spores. In old cultures 

 the organisms may 

 present great variety in 

 size and shape. Some 

 are irregularly twisted 

 filaments, sometimes 

 globose, sometimes 

 clubbed at their ex- 

 tremities, and also show- 

 ing irregular swellings 

 along their course; 

 others are short and 



thick, and may have the appearance of large cocci, often stain- 

 ing faintly. All these 



changes in appearance 



are to be classed together 



as involution forma. 



(Fig. 137.) 



Stainin//. — Cholera 



spirilla stain readily with 



the usual basic aniline 



stains, though Loffler's 



methylene-blue or weak 



carbol-fuchsin is speci- 

 ally suitable. They are 



Gram-negative. 



Distribution within 



the Body.— The chief 



fact in this connection 



is that the spirilla are 



practically confined to 



the intestine. Recent 



observations show that 



they may be found some- 

 times in the internal organs, and especially in the gall-bladder and 



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Fig. 137. — Cholera spirilla from an old agar 

 culture, showing irregularities in size and 

 shape, with numerous faintly - stained 

 coccoid bodies — involution forms. 

 Stained with fuchsin. x 1000. 



